Disposable culture device

ABSTRACT

A disposable culture device for determining the presence of bacteria, particularly in a sample of urine, the device comprising a container having a receptacle therein for solid culture medium, the suspected sample being poured into the container to inoculate the medium, the excess sample being discarded. The container thereby comprises an independent enclosure for incubation and bacterial colony growth.

United States Patent [191 Winter et al.

[ June 11, 1974 Henderson 195/ l 39 Andelin 195/139 Primary Examiner-Lionel M. Shapiro Assistant ExaminerRobert J. Warden Attorney, Agent, or FirmRobert L. Niblack; Gildo E. Fato 7 ABSTRACT A disposable culture device for determining the presence of bacteria, particularly in a sample of urine, the device comprising a container having a receptacle therein for solid culture medium, the suspected sample being poured into the container to inoculate the medium, the excess sample being discarded. The container thereby comprises an independent enclosure for incubation and bacterial colony growth.

6 Claims, 5 Drawing Figures PATENTEDJUI 1 1 an E5! VIII/Il/l/l/ DISPOSABLE CULTURE DEVICE BACKGROUND OF THE INVENTION Many methods of detecting bacteriuria have been described. One of the initial methods was to coat a microscope slide on both sides with medium. The slide was then dipped in the suspected sample and incubated and the growth on the medium was thereafter compared with photographs to obtain the bacterial count. In some diagnostic kits, the microscope slide hss been replaced with a paddle coated with media. For convenience, the paddle is occasionally affixed to the cap of the sample container. With this type of kit, a relatively large sample of urine is required, i.e., enough to entirely cover the paddle and difficulty is sometimes encountered with adequate drainage of the sample from the paddle. If proper drainage is not achieved, too much bacterial growth results. 1

SUMMARY OF THE INVENTION The present invention comprises a disposable culture assembly for testingfor the presence of bacteria and comprises a cup-like container having a flat bottom with a receptacle formed therein for containing solid culture medium; a cover adapted to close said container with a friction fit and comprising a disk having a horizontally extending portion, a raised central portion and a depending skirt around the periphery of the horizontal portion; and a foil-type seal affixed to the cup-like container.

The diagnostic kit of the present invention is particularly, adapted to aid the physician in making a simple determination of significant, bacteriuria. Bacteria in urine is diagnostic of urinary tract infection when the level of bacteria per milliliter of urine is in the range of 100,000 or greater. Furthermore, 87 to 95% of the bacteria isolated from such cases of infection fall within six genera which are E. coli, Proteus, Pseudomonas, Kleb- Siella-Enlerobacter, Streptococcus and Staphylococcus. The present diagnostic device utilizes an agar medium specially developed to promote the growth of these six microorganisms. 1

With the culture device of the present invention, only a small amount of suspected sample is required and the container within which the sample is collected is not important since it is not necessary to submerge a paddle within the container. The test is simple to conduct and therefore can be used in the physicians office to detect urinary tract infection. Particularly, obstetricians and pediatricians who encounter case after case of bacteriuria can conduct the test in routine fashion. Furthermore, the culture device provides a good shelf life because of the slow dehydration of the medium within the container of this invention.

Inoculation of the medium may be achieved by pouring a small amount of sample into the container, discarding the excess sample, replacing the cover and then incubating the container, preferably in the vertical position to ensure adequate drainage of the sample from the medium. After incubation, the growth can be determined and hence the presence of infection. Significant bacteriuria is generally considered to be present when the level ofbacteria per milliliter of urine is 100,000 or greater. A count of between 10,000 and 100,000 microorganisms per milliliter represents possible bacteriuria and a count of less than 10,000 is probably due to contamination of the sample.

DESCRIPTION OF THE DRAWINGS The invention will be described in greater detail with reference to the drawings in which:

FIG. 1 is a perspective view of the culture device of the present invention illustrated in exploded fashion;

FIG. 2 is a fragmentary sectional view of the cover taken along the line 2-2 of FIG. 1;

FIG. 2a is a fragmentary top elevational view of the cover illustrated in FIG. 2;

FIG. 3 is a fragmentary sectional view of the container taken along the line 3-3 of FIG. 1; and

FIG. 4 is a sectional side view of the culture device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in FIG. 1, the culture device 10 comprises a cup-like container 1 l, a cover 30 and a seal 40. The container 11 includes a flat bottom 12 and an upstanding wall 13 with a horizontal flange 14extending from the edge of the wall 13, a receptacle 15 being formed inthe bottom 12 of the container 11 for retention of solid culture medium 16. As illustrated, the receptacle 15 is formed by an annular ridge l7 spaced away from the upstanding wall 13 to form an annular space 18 along the wall to receive the cover 30 and provide for urine drainage as hereinafter explained. To facilitate the counting of any colonies which may form, grid lines 19' can likewise be formed in the bottom of the container within the receptacle defined by the annular ridge 17, the grid lines 19 being visible through the agar gel 16. As is apparent in FIGS. 3 and 4, the grid lines 19 are preferably of a lesser height than the annular ridge 17 to permit the liquid medium 16 to flow readily throughout the entire receptacle 15. A grid height of 10 thousands of an inch will permit the agar 16 to readily flow over the grid lines 19. To prevent loosening of the agar gel 16 from the bottom 12 of the container 11 during shipment and handling, which could result in the formation of air pocketsthereby making observation of any colonies which may form somewhat difficult; several inwardly projecting nibs 21 or locks are formed in the anngular ridge 17 to assist in retaining the gel 16. To aid in retaining the cover 30, several nibs 20 can be formed in the wall 13 of the container 11 adjacent the bottom 12 and projecting inwardly.

To protect the medium 16 from contamination, particularly during incubation, the cover 30 is placed over the medium 16. The cover 30 comprises a disk 31 having a horizontally extending portion 32 with a raised central portion 33 and a skirt 34 depending from the periphery 35 of the disk 31. Again, to aid in retaining the cover 30 within the container 11, a projecting foot 36 can be formed around the bottom edge 37 of the skirt 34, the foot 36 fitting against the nibs 20. Likewise, by forming the skirt 34 at a slight angle with relation to the horizontal portion 32, the cover 30 can be retained within the container 11 by friction alone. The raised central portion 33 facilitates removal and replacement of the cover 30. Accordingly, the walls 38 of the raised central portion 33 are spaced from the wall 13 of the container 11 sufficiently to permit insertion of the fingers. To aid gripping, spaced ribs 39 can After the medium 16 is placed in the receptacle 15 and the cover 30 is put in place, an overseal 40 is hermetically heat sealed to the horizontal flange 14 on the container 11 to seal the device and preserve its sterility during transportation and storage. Prior to applying the overseal 40 to the device 10, the container 11, cover 30 and overseal 40 are gas sterilized using known methods and the receptacle aseptically filled with medium 16. Preferably, the overseal 40 comprises a lamination of foil and paper with a heat-seal coating on the foil. Such a construction affords the best moisture retention as well as permitting excellent printing reproduction on the paper portion for any required instructions and the like. A tab 41 is formed in the overseal40 for ease of removal. For identification purposes, each culture device 10 must retain throughout the test, the patients name and the date the sample was collected. Accordingly, a self-adhesive label (not shown) can be affixed to the undersurface of the bottom 12 of the container 11.

Since agar gels tend to lose moisture; one problem with culture devices of this type is dehydration of the medium. The culture device 10 of the present invention however provides excellent stability. In an accelerated stability test, twenty culture devices 10 were aseptically filled with medium 16, covered and sealed. They were The weight loss per agar weight after a period of four weeks at the noted conditions was found to be 0.7 percent. In contrast, the weight loss per agar weight contained in a screw cap glass bottle was found to be 2.0 percent and in a snap top plastic vial, 53.4 percent. The excellent stability of the culture device 10 of the present invention results from the foil overseal 40 and the polypropylene, injection molded container 11, which combination provides good moisture retention for the agar or medium 16. If desired, the container 11 can be molded from a clear plastic such as styrene or XT polymer or a translucent plastic like unpigmented polypropylene to yield a clear package. When the culture device 10 is employed for the detection of urinary tract infection, or in any test wherein the resultant bacterial colonies are light in color, an opaque container 11 is preferred in order to provide the best contrast with the bacterial colonies for ease of observation. The cover 30 can be injection molded from styrene to provide clarity so that if desired, colony growth can be observed directly through the cover 30.

A suitable medium formulation to be contained within the receptacle 15 of the container 11 and which will support the growth of all of the six organisms generally responsible for urinary tract infections is as follows:

Sucrose gms BBL Myosute l0 gms BBL Biosate 10 gms Difco Beef Extract 2 gms Difco Agar gms H O i000 mls BBL: Division of Bio-Quest, Division of BectonDickinson & Co. Difco: Difco Laboratories, lnc.

moving and discarding the overseal 40. The cover 30 is snapped apart from the container 11 and lifted out. A small portion of a suspected sample of urine is poured into the container 11 sufficient to cover the surface of the medium 16 to assure complete inoculation thereof. As soon as the surface of the medium 16 is covered, the urine sample is swirled about and then poured off. The cover 30 is then replaced and the culture device 10 is incubated in a verticle position to ensure complete drainage of the urine sample from the medium 16. As previously noted, the cover 30 fits within an annular space 18 between the receptacle 15 in the bottom 12 of the container 11 and the wall 13. The annular space 18 is more than wide enough to receive the cover 30 so that it can function as a urine drainage area. Even though the urine sample is discarded after the medium 16 is innoculated, droplets can cling to the agar surface. By incubating the container 11 so that the surface of the medium 16 is in a vertical position, any droplets will run off into the annular space 18. The culture device 10 is incubated in this position at a temperature of 37 C for a minimum of 15-18 hours but not longer than 24 hours. After incubation, any growth on the surface of the medium 16 is observed and a quantitation made. Quantitation is accomplished by counting the colonies that have grown on the surface of the medium 16. Each colony represents approximately 1,000 microorganisms per milliliter of urine. Colonies or more, equivalent to 100,000 microorganisms or more per milliliter, repre sent significant bacteriuria. l0 to 100 Colonies, 10,000 to 100,000 microorganisms per milliliter, represents possible bacteriuria, and less than 10 colonies represent no significant bacteriuria and may be the result of contamination of the sample. If significant bacteriuria is indicated, the patient can be referred to a clinical laboratory for further testing to determine the specific infecting organism or organisms. In the event of possible bacteriuria, the screening test should be repeated as indicated above. If results of the second test again indicate 10,000 or more microorganisms per milliliter, then the patient can be referred to a clinical laboratory for further testing. If less than 10,000 microorganisms per milliliter is indicated, no further testing is necessary. Alternatively, quantitation can be ascertained by a visual comparison of the resultant colony growth with known colony density photographs. After the results of the test are recorded, the culture device 10 can be discarded.

If identification of the microorganism responsible for the infection is desired, rather than discarding the culture device 10, it can be used as a source of innoculum for further testing. Likewise, after incubation, the culture device 10 can be used for the determination of the antibiotic sensitivity of the microorganism.

What is claimed is:

l. A disposable culture assembly for testing for the presence of bacteria comprising:

a cup-like container having a fiat bottom and upstanding wall, said wall defining a closed end and an open end;

a receptacle for containing solid culture medium therein formed in the bottom of the container;

said receptacle being spaced away from the upstanding wall to form an annular space along the wall to receive a cover;

and a cover adapted to fit in said container to close said container with a friction fit comprising a disk having a raised central portion and a depending skirt around the periphery thereof;

the depending skirt fitting within the annular space and engaging the upstanding wall to close the container and the raised central portion arranged for gripping for removal of the cover.

2. The culture assembly of claim 1 wherein the receptacle includes grid lines arranged therein to facilitate the counting of any bacterial colonies that may form on the culture medium.

3. The culture assembly of claim 1 including a horizontal flange projecting from said upstanding wall of the container at the open end thereof.

4. The culture assembly of claim 3 including an overseal sealed to the horizontal flange of the container to seal the assembly and preserve sterility during transportation and storage.

5. The culture assembly of claim 4 wherein the overseal comprises a lamination of foil and paper, with a heat-seal coating on the foil for sealing the overseal to the container.

6. The culture assembly of claim 5 wherein the raised central portion of the cover includes a plurality of spaced ribs in the wall thereof to aid gripping of the COVCI. 

2. The culture assembly of claim 1 wherein the receptacle includes grid lines arranged therein to facilitate the counting of any bacterial colonies that may form on the culture medium.
 3. The culture assembly of claim 1 including a horizontal flange projecting from said upstanding wall of the container at the open end thereof.
 4. The culture assembly of claim 3 including an overseal sealed to the horizontal flange of the container to seal the assembly and preserve sterility during transportation and storage.
 5. The culture assembly of claim 4 wherein the overseal comprises a lamination of foil and paper, with a heat-seal coating on the foil for sealing the overseal to the container.
 6. The culture assembly of claim 5 wherein the raised central portion of the cover includes a plurality of spaced ribs in the wall thereof to aid gripping of the cover. 